Spinner spreaders for granular, i.e. flowable material are well known in the art, for agricultural application, lawn care and road maintenance application. Typically, such spreaders are mounted onto a truck body, truck chassis, trailer, or slid into a truck's dump body. The spreader includes a material storage bin(s), a conveyor system(s), metering method, and rotating spinners. The conveyor systems transfer material from the storage bin(s) to the spinners. The spinners broadcast the material across the field, lawn, or road. Usually a single spinner or a pair of laterally spaced spinners are provided with a material divider plate positioned above the spinners to direct the material from the discharge end of the conveying means onto the spinners.
Many factors influence the spreading of granular materials and uniform distribution of the particles. They include the size, shape, hardness, density, and volumetric flow rate of the material particles. The diameter of the spinner disk or fan, the speed of the spinner disk, the radial angle of the fins, the loft angle, friction factors also among others that influence the spreading of material. As taught in U.S. Pat. No. 6,517,281 to Rissi, many of these factors can be accounted for by adjusting the drop point of material onto the spinning disks. This patent is hereby incorporated herein in its entirety by this reference.
Spreader manufacturers are constantly trying to improve the value of their spreaders by increasing the amount of acres spread per hour. The vehicles carrying or towing the spreader are operating at a higher speed to cover more acres per day. More importantly, the manufacturers are developing spreaders capable of uniform symmetrical distribution over a wider swath width. Wider patterns result in less use of expensive fuel, less soil compaction, and less time spent spreading each acre. The result is a significantly higher return on investment for those using this equipment. These types of spreaders are typically broadcast spreaders with two spinner disks.
Global positioning systems (GPS) and automatic steering systems are able to guide the vehicles accurately through field and help maintain uniform coverage of materials. However, in order to cover the field area completely, the wider spread patterns of a broadcast spreader make it difficult to avoid overlapping areas or spreading into areas that should be avoided. Likewise, spreading on irregular shaped fields may result in inadequate coverage when the spreading vehicle is approaching areas at an angle that is not perpendicular to areas already covered. The difference in an overlapping area to an area without coverage will show significantly as plants are growing. In most cases, the applicator makes sure that all areas are covered rather than skipping small areas that are inefficient to cover. This results in using more fertilizer and higher costs.
To some extent, the width of a symmetrical pattern with regard to the center line of the carrying or towing vehicle can be reduced by simply decreasing the amount of metered material conveyed to the spinner in proportion to the reduced width in combination with reducing the spinner rpm to throw the particles less distance. High throughput spreaders producing wide flat top patterns produce results with some compromise to a uniform spread distribution unless the drop point of material onto the spinner disks can be adjusted as taught in the '281 Rissi patent. European spreaders typically producing a pyramid spread pattern can likewise reduce the material flow and the spinner speed to result in a lesser width.
Spreaders producing wide flat top patterns have the most abrupt decline of the spread pattern at the outside edges of the distribution. Because of this abrupt fall off of the pattern, flat top patterns require the least amount of edge overlap to produce a uniform distribution. At the same time, too much overlap of these spreaders quickly produce areas that can double the intended rate per area. Spreaders producing pyramid patterns have a generally declining distribution from the centerline to the outside edges and require an overlap equal to half of the total width. Pyramid pattern spreader overlap errors have a more gradual effect.
When spreading the outside perimeter of a field, flat top patterns also have a distinct advantage over the pyramid pattern because of the more abrupt cutoff. To aid spreading around the perimeter of the field, pyramid pattern spreaders usually use a combination of mechanical deflectors, reduced spinner speed, and reduced flow to produce an acceptable reduced width boundary condition at one side of the centerline of the carrying or towing vehicle.
Many of the pyramid pattern spreaders utilizing two spinner disks are gravity fed. These spreaders rely on accurate placement of fertilizer on to the spinner disk through an orifice directly above each spinner. The throughput of these spreaders are limited by how fast the material can gravity flow from a funnel shaped bin through the restrictive orifice and on to the spinner. While they can produce a wide pyramid pattern and the flow can be adjusted easily, the orifice limits the speed of the carrying or towing vehicle and overall throughput.
Many of the flat top pattern spinner spreaders rely on accurate placement of fertilizer across a larger radial portion of the fins on the spinner disk. As in the '281 patent, this accurate placement is accomplished by positioning the spinners under a fixed drop edge. Material conveyed from a bin can fall onto the guiding drop edge without being restricted by a gravity fed orifice at the bottom of a bin. These spreaders can produce a wide flat top pattern with the conveying system capable of high flow rates and high overall throughput.
The twin spinner gravity fed spreaders have an advantage of varying the flow rate to each spinner by adjusting individual orifices. If an asymmetrical pattern is desired for a field boundary condition, an angled headland, an irregular field profile, or a narrowed swath, the orifice is reduced and the spinner speed is lowered to maintain the distribution rate for the narrower side of the spread pattern. To accomplish the same in a twin spinner conveyor fed spreader, some manufacturers have tried to position a split gate upstream from the conveyor end. Another way of reducing the flow to one spinner is to provide twin conveyors capable of varying the amount of flow to each spinner. Doing so requires independent control of each conveyor.
It is common for present day spinner spreaders to have multiple product bins with conveying or metering systems for each bin. This allows the user to spread multiple fertilizer or seeding products in one pass down the field while constantly varying the outputs to match the needs or capabilities of the soil, thus producing the highest yield for the least amount of input costs and gives the farmer a higher return on investment.
As taught in the U.S. Pat. No. 6,817,551 to Williams et al, having the conveyors of each bin meter directly into a common material gravity flow column allows multiple products to be mixed without any other delay in transport. For common thinking, combining multiple bins of a conveyor fed twin spinner spreader with the need to meter the product independently to each spinner would require a split conveyor for each bin. While electronics and software can easily control doubling the number of conveyor systems, the doubling of hydraulic motors, hydraulic valves, sensors, conveyors, bearings, drive shafts, etc. are expensive, add weight to the spreader, add volume to the drive components and take away usable volume for the spreader bins, hurt hydraulic efficiencies, etc. The increase in mechanical and hydraulic parts increase repair items and the dense packaging of those components would make access to the repair items more difficult.
Another way of solving the problem is to have independent upstream orifice control, commonly accomplished and referred to as a feed gate, which could meter material independently from each bin unto conveyors feeding each spinner. This also creates a doubling of mechanisms and requires movement of the gate to meter the correct amount of product. Having the orifice upstream creates the need to “look ahead” for the controls to anticipate changes in the swath width and there is the need to determine master and slave relationships between the conveyors and gates as metering is accomplished by both speed and opening.
The increased swath widths and the limitations of conventional dual spinner prior art create the need for a simple method of metering product flow from each spinner spreader conveyor bin to produce asymmetrical flow to each spinner to match asymmetrical spreading conditions required for various field boundary conditions.
Furthermore, there is also a need to create a simple method to place product onto the spinner disk in a manner to permit spreading to one side of the spreading vehicle allowing the product to be spread into a field from a road, tramline, or as the spreader is approaching a headland at a non-perpendicular angle.
The need for a simple method to do the above also needs to be accomplished with minimum compromise to the spread pattern coefficient of variation or restriction to the material flow.